Does Love Depend on Blood Type?

If you want to know if he loves you so, a new study suggests that the secret may not be in his kiss, but in his far less romantic-sounding blood levels of oxytocin.

According to the study, published in Psychoneuroendocrinology,higher levels of oxytocin — the hormone known as the “cuddle chemical,” which rises during breast-feeding, lovemaking and parent-child bonding — were associated with more emotional responsiveness between couples and predicted which couples would stay together longer than others.

The study involved 163 adults in their 20s. Of the participants, 120 were new couples who had just started a romantic relationship; the rest were singles. Researchers found that people in the throes of new love had far higher levels of oxytocin than the unpartnered did. And higher oxytocin levels were linked with more affectionate touch, better moods and greater synchrony of movements between couples.

What’s more, couples with the highest levels of the hormone early on were more likely to stay together, compared with those with lower levels — at least based on the 25 couples who were still together and with whom the researchers were able to follow up six months later.